[Properties of fast-adapting receptors of the lungs in the cat]

Out of 44 rapidly adapting lung receptors in vagotomized cats, 34 (77%) revealed spike activity in quiet breathing whereas 10 terminals (23%) had no spontaneous activity but revealed it in deep breathing. Firing rate was by 2.7 times more in inspiration as compared to expiration, the greatest amount of APs being registered, at that, in the second half of inspiration or expiration. Occlusion of the trachea in the end of expiration decreases by 2.2 times the firing rate both in inspiration and expiration as compared to spontaneous breathing. A number of receptors revealed a weak impulse activity at a relatively constant lung volume; the average firing rate with occlusion of the trachea is 2.4/sec whereas in inflation of the lungs with the 40 ml and 100 ml volumes the average firing rate was 4.5/sec and 9.8/sec, resp. The discharges of the rapidly adapting receptors seem rather insignificantly if at all affect the course of quiet inspiration, but to take part in regulation of the expiration duration.